This invention relates to pressure sensitive adhesives. More particularly, this invention relates to pressure sensitive adhesives containing a blend of intermediate pressure sensitive adhesives.
The term, pressure sensitive adhesive, as used herein, refers to adhesives that can be adhered to a surface and yet can be stripped from the surface without transferring more than trace quantities of adhesive to the surface, and then can be readhered to the same or another surface because the adhesive retains some or all of its tack and adhesive strength.
Silicone pressure sensitive adhesive (PSA) compositions are known in the art. Reference is made, for example, to U.S. Pat. Nos. 2,857,356; 2,736,721; 2,814,601; 4,831,080; 4,882,377; and 4,309,520.
U.S. Pat. No. 2,676,182 (Daudt et al.) discloses a method for preparing a resin copolymer containing M and Q units and soluble in aromatic solvents, wherein a silica hydrosol is reacted under acidic conditions with organosubstituted siloxanes.
U.S. Pat. No. 2,736,721 (Dexter) discloses a pressure sensitive adhesive composition and method of preparing it, the composition comprising 5 to 70 per cent by weight of a benzene soluble copolymer and 95 to 30 per cent by weight of a benzene soluble organosiloxane.
U.S. Pat. No. 2,814,601 (Currie et al.) discloses a pressure sensitive adhesive containing 40 to 75% by weight of a benzene soluble resin copolymer and 25 to 60% by weight of a hydroxy end-blocked diorganopolysiloxane fluid. This patent is cited in the instant application because of its disclosure of a method for preparing polydiorganosiloxanes.
U.S. Pat. No. 2,857,356 (Goodwin) discloses a pressure sensitive adhesive composition prepared from the intercondensation of a mixture containing (1) a cohydrolysis product of a trialkyl hydrolyzable silane and alkyl silicate and (2) a linear, high viscosity organopolysiloxane fluid containing terminal silicon-bonded hydroxy groups.
U.S. Pat. No. 4,309,520 (Blizzard) discloses a pressure sensitive adhesive containing a resin, polymer, and a cluster compound.
U.S. Pat. No. 4,882,377 (Sweet et al.) discloses a pressure sensitive silicone elastomer composition containing (I) a silicone pressure sensitive adhesive composition containing from 35 to 70 parts by weight of a benzene-soluble resinous copolymer and from 30 to about 65 parts by weight of a polydiorganosiloxane, (II) a cross-linkable silicone elastomer, and (III) a viscosity reducing agent.
U.S. Pat. No. 4,831,080 (Blizzard et al.) discloses a pressure sensitive adhesive composition prepared by reacting (I) a pressure sensitive adhesive; (II) a liquid organohydrogenpolysiloxane; (III) the pressure sensitive adhesive of component I; and (IV) a cure agent for the liquid
U.S. Pat. No. 4,906,695 (Blizzard et al.) a pressure sensitive adhesive prepared by reacting a first component containing a pressure sensitive adhesive and an alkoxy-functional silicon compound with a second component containing the pressure sensitive adhesive of component I and a cure agent for the alkoxy-functional silicon compound.
Silicone pressure sensitive adhesives are widely employed in a variety of uses, including as pressure-sensitive tapes. Silicone pressure-sensitive adhesives exhibit excellent adhesion to very low energy surfaces, have excellent weatherability, are flexible at low temperature and are chemically stable at very high temperatures.
Although many silicone-based pressure-sensitive adhesives are known in the art, it is continually desired to provide improved pressure sensitive adhesives having superior peel strength, consistently high tack, and increased high-temperature performance. The composition of this invention provides improved silicone pressure-sensitive adhesives having these desirable properties.